Add additional exclude property

The default value of `spring.devtools.restart.exclude` is quite long and
any override requires to copy/paste it to add additional exclusions. To
avoid that, a new `spring.devtools.restart.additional-exclude` property
has been added.

Both properties are now used to compute the full list of exclusions that
is used by PatternClassPathRestartStrategy.

Closes gh-3774

spring-boot-devtools/src/test/java/org/springframework/boot/devtools/autoconfigure/DevToolsPropertiesTests.java

@@ -0,0 +1,58 @@
+/*
+ * Copyright 2012-2015 the original author or authors.
+ *
+ * Licensed under the Apache License, Version 2.0 (the "License");
+ * you may not use this file except in compliance with the License.
+ * You may obtain a copy of the License at
+ *
+ *      http://www.apache.org/licenses/LICENSE-2.0
+ *
+ * Unless required by applicable law or agreed to in writing, software
+ * distributed under the License is distributed on an "AS IS" BASIS,
+ * WITHOUT WARRANTIES OR CONDITIONS OF ANY KIND, either express or implied.
+ * See the License for the specific language governing permissions and
+ * limitations under the License.
+ */
+
+package org.springframework.boot.devtools.autoconfigure;
+
+import org.junit.Test;
+
+import static org.hamcrest.Matchers.arrayContaining;
+import static org.junit.Assert.assertThat;
+
+/**
+ * Tests for {@link DevToolsProperties}.
+ *
+ * @author Stephane Nicoll
+ */
+public class DevToolsPropertiesTests {
+
+	private final DevToolsProperties devToolsProperties = new DevToolsProperties();
+
+	@Test
+	public void additionalExcludeKeepsDefaults() {
+		DevToolsProperties.Restart restart = this.devToolsProperties.getRestart();
+		restart.setAdditionalExclude("foo/**,bar/**");
+		assertThat(restart.getAllExclude(), arrayContaining("META-INF/maven/**",
+				"META-INF/resources/**", "resources/**", "static/**", "public/**",
+				"templates/**", "foo/**", "bar/**"));
+	}
+
+	@Test
+	public void additionalExcludeNoDefault() {
+		DevToolsProperties.Restart restart = this.devToolsProperties.getRestart();
+		restart.setExclude("");
+		restart.setAdditionalExclude("foo/**,bar/**");
+		assertThat(restart.getAllExclude(), arrayContaining("foo/**", "bar/**"));
+	}
+
+	@Test
+	public void additionalExcludeCustomDefault() {
+		DevToolsProperties.Restart restart = this.devToolsProperties.getRestart();
+		restart.setExclude("biz/**");
+		restart.setAdditionalExclude("foo/**,bar/**");
+		assertThat(restart.getAllExclude(), arrayContaining("biz/**", "foo/**", "bar/**"));
+	}
+
+}